Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a first image of a display screen or portion thereof with a transitional graphical user interface, showing our new design.

FIG. 2 is a front view of a second image of the display screen or portion thereof with the transitional graphical user interface.

FIG. 3 is a front view of a third image of the display screen or portion thereof with the transitional graphical user interface.

FIG. 4 is a front view of a fourth image of the display screen or portion thereof with the transitional graphical user interface.

FIG. 5 is a front view of a fifth image of the display screen or portion thereof with the transitional graphical user interface.

FIG. 6 is a front view of a sixth image of the display screen or portion thereof with the transitional graphical user interface; and,

FIG. 7 is a front view of a seventh image of the display screen or portion thereof with the transitional graphical user interface.

The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-7. The process or period in which one image transitions to another image forms no part of the claimed design.

The stippling shown in FIGS. 2-7 illustrates a contrast in appearance.

The broken line showing of the display screen forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a transitional graphical user interface, as shown and described. 